1. Field of the Invention
The invention relates generally to the field of optical coherence tomography and applications thereof. Specifically, the invention relates generally to methods and systems for collecting and processing three-dimensional (3D) data or two-dimensional (2D) images in ophthalmology.
2. Description of Related Art
Optical Coherence Tomography (OCT) is an optical signal and processing technique that captures three-dimensional (3D) data sets with micrometer resolution. The OCT imaging modality has been commonly used for non-invasive imaging of an object of interest, such as cornea and retina of the human eye, over the past 15 years. A cross sectional retinal image from an OCT scan allows users and clinicians to evaluate various kinds of ocular pathologies in the field of ophthalmology. However, due to limitations of scan speed in imaging devices based on time-domain technology (TD-OCT), only a very limited number of cross-sectional images can be obtained for evaluation and examination of the entire retina.
In a new generation of OCT technology, Fourier-Domain or Spectral Domain Optical Coherence Tomography (FD/SD-OCT) has significantly improved over TD-OCT with, for example, better scan speeds and resolution. 3D data sets with dense raster scan or repeated cross-sectional scans can now be achieved by FD-OCT with a typical scan rate of approximately 17,000 to 40,000 A-scans per second.
These technological advances in OCT enable massive amounts of data to be generated at an ever increasing rate. As a result of these developments, myriad scan patterns were designed and employed to capture various volumes of interest (VOI) of the eye to enhance diagnostic capabilities.
Current trends in OCT ophthalmology make extensive use of 3D imaging and image processing techniques to obtain and process 3D data. The 3D data can be utilized for diagnosing diseases such as glaucoma, age-related macular degeneration (AMD), corneal diseases, and other medical conditions affecting the eye. Analyses of OCT data have been mostly focused on thickness measures of various segmented layers in the cornea and the retina. However, ocular diseases may affect the scattering properties of ocular tissues without changing the thickness measures. Some other physical characteristics and properties of the cellular layers of the eye can provide additional information useful for evaluations and diagnosis of different eye conditions.
Involuntary motions of the subject's eye during OCT data acquisition commonly create artifacts that can impact the accuracy and reliability of the physical characteristics and properties of the VOL. These motions introduce relative displacements of the acquired data; for example, physical features could appear discontinuous in the resulting 3D data and might deviate from the true anatomy of the eye, resulting in unreliable and inaccurate processing and evaluation.
It is common in the arts to perform diagnosis of ophthalmic diseases based on qualitative visual impressions and/or quantitative computer-aided diagnosis (CAD) analysis. Therefore, it is important to employ one or more processing methods to ensure the acquired 3D data and the extracted features remain consistent and readily comparable due to differences in system to system or modality to modality variations. There is a need for systems that improve the accuracy and effectiveness of the processing and evaluation of OCT data.